Both Engines Limited to 9,000 RPM, WHY?

[Ronnie]

The non ho engine is a 998 cc with 140 hp, the ho is a 1,052 cc with 160 hp. Another member verified that the blocks are the same not sure about everything else but think the ecus are different as well.

 

[bronze_10]

So the main physical difference must be in the piston stroke if it is the same block... then everything else is engine parameters from the ecu I guess..

 

[Scottintexas]

here is the thread about some who did the swap,
https://jetboaters.net/threads/110hp-block-is-interchangable-with-the-160hp-block.1595/

 

[Bruce]

So in following this thread a qhestion comes to mine about the standard verses high out put mr1.... is the only different the rpm limiter that determines the overall horse power output? Could you take a non ho and change the Rev limiter to
10k and then it suddenly produces the same as the ho? And I assume the ecu is what regulates that...

In this case the engine is physically smaller. I believe it is 998 while the later engines are 1052.

 

[bronze_10]

Physically smaller but the same block?

 

[swatski]

Guys, just to give my opinion.
The issue of upgrading non-HO to HO MR-1s has been debated extensively, as you can imagine, in the greenhulk community -- these were the most popular engines in all yamaha skis for a long time.
Without getting into details, the answer is NO. It can be done, but requires swapping too many internals.
Similarly, a 1.8l N/A engine can not be upgraded to SHO or SVHO, can be done in theory, but it would be less expensive to buy a new engine. (And yes, I did look into it...)

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[bronze_10]

Guys, just to give my opinion.
The issue of upgrading non-HO to HO MR-1s has been debated extensively, as you can imagine, in the greenhulk community -- these were the most popular engines in all yamaha skis for a long time.
Without getting into details, the answer is NO. It can be done, but requires swapping too many internals.
Similarly, a 1.8l N/A engine can not be upgraded to SHO or SVHO, can be done in theory, but it would be less expensive to buy a new engine. (And yes, I did look into it...)

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I didn't want to derail the thread but I was just wondering..

 

[swatski]

He did clarify these were not my boat. I researched the impeller part numbers myself for the SRT-1000D engine that I have and they match. They also match what Bruce suggested. I'm confident these are the stock and correct impellers.

BTW: this is how much oil I removed from the 2 engines today after just recently having a pro change the oil. The dipsticks now just read oil on the very tips. I also noticed what looks like a hole in the intake boxes to allow air into the oil chamber. If that's where the oil is getting into the intake it's no wonder the level needs to be kept so low.
View attachment 44483

Going to the lake tomorrow. Hopefully I'll have a little more power and top end and the oil will stay out of the intakes.

I'm not familiar with MR-1s much, but does that look like A LOT of DIRTY oil?
the opening you are referring to may be an oil breather (with the hose going to the air filter), I was taught that the oil vapors from engine help to lubricate throttle body, the intake valves, other parts, do you guys agree?

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[swatski]

Okay I have the pumps apart and here are pictures of the numbers and the condition (Starboard first 2, Port second 2). They sure look like factory and appear to match the numbers Bruce provided. The only flaw I see is one obvious ding in the trailing edge of the port impeller from a rock. The bearings turn free and smooth on both shafts and are tight in the housing. I also added a photo of the Port shaft that has been rubbing on white nylon bushing where it enters the fiberglass hull. I have no idea what turned the bushing blue.
View attachment 44464 View attachment 44465 View attachment 44466 View attachment 44467 View attachment 44468
Port bushingView attachment 44469
Starboard bushingView attachment 44470

@AZ Native I don't know, to me this looks like a basically PRISTINE condition setup! (I mean, good looking pump!)

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[AZDANSX230HO]

At this point I am wondering if the oil that entered the throttle bodies from the oil in the air filters messed up a sensor? I had an aftermarket K&N Filter on a vehicle in the past and it had too much oil on the filter from the factory and it played hell with my mass air flow sensor. You might want to spray some throttle body cleaner in each of the intakes to see if it helps and look for any sensors that could have been affected by oil coming in contact. If there is in fact a mass air flow sensor, that takes a special type of cleaner to clean it. I would also run some fuel injector cleaner through it as well, previous owner could have used a crappy brand of fuel.

I tried looking at the parts fiche and there are a couple sensors, but the explanation of the parts are not very clear:

65L-85886-00-00 THERMOSENSOR

60E-82380-10-00 SENSOR, PRESSURE

60E-85885-10-00 THROTTLE SENSOR ASSY

60E-13660-00-00 BY-PASS VALVE MOTOR ASSY

 

[AZ Native]

We have some progress. Took the boat out today and got as high as about 9,400 RPM out of the Starboard and 9,800 out of the Port engine. That's 400 and 800 RPM better than previous. This produced between 40 and 43 MPH depending on water condition. After the oil warmed up I checked the level on the lake and had to add back about 1/3 quart to each engine. Checked again after a hard run and now the hot oil shows at the low mark, both engines. Looks like getting the oil cleaned out of the intake box coupled with new air filters and proper level made a difference. I've also been running Yamaha Engine Med RX in the gas for the last few outings per instructions from the dealer (like pouring liquid gold in the tank, probably a waste of $$ on low hour engines).

I'd love to get the Starboard engine up to 9,800 so I don't have to pull back the Port so much to match RPM's. Now that I know the pumps are fine, I will concentrate on tuning the engines. Frankly I'd be good with 9,800 out of both engines and call it good enough. Maybe all that oil running through the intake took it's toll.

I put Brisk plugs in my jet skis and Polaris Ranger (nice improvements). I'm thinking they may add an incremental performance boost to the MR-1 engines. But at $18 each...

I will pose a new observation and thought. At WOT the boat want's to pull to port with RPM's matched on both engines. I didn't think to try running the Port engine wide open 400 RPM ahead of the Starboard. At lower speeds I try to sync the RMP's, but does it hurt to run WOT at different RPM's??

 

[bronze_10]

On my boat the starboard engine spins at 10600 rpm and the port at 10200... when I asked a long time ago about the difference someone of the forum explained a small difference between the two engines is normal at wot due to different load dynamics or some other really large words.... when I run mine at wot I can't feel the boat pulling even with 400 rpm difference... but I don't do wot much... just from time to time to keep the engines healthy, then back to the nice slow cruise....

 

[AZ Native]

I checked the oil level again yesterday and both engines show at the Low mark when cold. That's the same level I read on the water with hot engines. Also the intake boxes are soaked with oil again. At least the new air filters only show a little oil splatter on them. I'm going to pull more oil out and clean up the intakes, but this is getting frustrating trying to keep oil out of the intakes. What gives Yamaha?? It's definitely impacting performance.

BTW AZDan, I can't find any evidence that these engines have a mass air flow sensor. I am going to get some intake cleaner though. All this oil getting sucked in over time has to have impacted some parts of the throttle body. This is way beyond my pay grade.

 

[Bruce]

You can remove the air filters for testing. There is not much dust on the water.

 

[AZ Native]

I finally made it to the lake today after pulling more oil out of the engines, cleaning up the intake boxes again and replacing the plugs again. Port is now hitting 9,800 and the starboard engine is getting 9,500 RPM at WOT. I took it up to WOT on several occasions and hit those numbers consistently. That's almost a significant 1,000 RPM improvement. We probably ran a couple hours total without degrading performance.

I'm going to chalk this up to too much oil in both engines. And I'm going to say it really doesn't take much oil to reach the point that it get's sucked in to the air box. I finally had to settle for just barely showing on the bottom of the dip stick when level and cold. And, I mean, just barely. Like 1/8 of an inch. I'll pull the air boxes apart after another outing in about a week, but I'm expecting it to stay clean now. I put new air filters in a month ago, removing might add another 100 RPM, but last time I did this the engines get too loud to tolerate.

I'd love to get the starboard engine to match the port, but we're running out of ideas and I'm afraid next steps will exceed my mechanical chops. I am willing to keep learning and trying ideas you may have. Thanks everyone for your help with this. I've learned a lot from your input and my experiments.

 

[AZ Native]

I was out again this weekend and still getting 9,800 out of the port and 9,900 out of the starboard engines. I still think this model should get 10,200. I noticed a sticker under the windshield that says California approved. Does this make it a CARB boat and does that mean it has some emissions modifications that may be slowing it down a little? I've read a little here about CARB, but I don't know when it started and what it really means for performance.

 

[Ronnie]

Carb boats started in 2012 on 1.8 liter 1,812 cc boats. If you have the 160 hp 1,052 cc engines you should be hitting 10,200 at sealevel this assumes your props and stock and not custom pitched.

 

[Bruce]

I was out again this weekend and still getting 9,800 out of the port and 9,900 out of the starboard engines. I still think this model should get 10,200.

I believe you 998cc engines are supposed to max out at 10,000 RPM. If so you are pretty close. If not, you are still pretty close.

 

[Bruce]

@Murf'n'surf, which engines do you have and what is their max RPM?

 

[AZ Native]

I believe you 998cc engines are supposed to max out at 10,000 RPM. If so you are pretty close. If not, you are still pretty close.

You're right I'm much closer now. I just didn't want to waste anymore time on trying to get a couple hundred more RPM out of the engines if it was made for California, the state that pretty much regulates the fun out of everything. More RPM's isn't just about going faster, in my case getting the engines back to original performance specs provided a major improvement in the hole shot for getting bigger skiers (like my 220 lb. frame) out of the water.