90 Tohatsu TLDI jet

[lots of boats]

I put a jet on a 90 TLDI, but I never could get it to turn at more than 4800 rpm. Does anyone have any sugestions for how to get it to turn up another 800 -1000rpm?

 

[tohatsutldi]

pitch

 

[chevyjet]

Re: 90 Tohatsu TLDI jet

Ya I had that problem too, with a 7 3/8" 90hp impeller all you can get at sea leavel is 4800 t0 4900..... real dog. If you put the impeller in a lathe and cut the top down you pick up revs, 5400 works good. Funny thing is if you use this same impeller in a merc 90 they run 5500 to 5600 , yamaha alittle less maybe 5400. I tried this on 3 diffrent TLDI moters and 4 boats, my conclusion after all that messing around was that the tldi 90 only has about 78 to 80 true hp. If you turn them at 5750 they preform not too bad but the fuel and especialy oil consumption is out of this world. Also if you run them with a jet you will have sand/trash pluging problems in the water cooling line going to the air pump, you have to take the elbow fitting out of the top of the pump and replace it with a straight hose barb.

Hope this helps

 

[lots of boats]

Re: 90 Tohatsu TLDI jet

Are there pitch or diameter options on stock impellers?

I have had jet pumps on other motors and it seems to me there are about five pump housing sizes and the75-150hp all use the same housing and impeller diameter.

The only thing I could adjust or change was the liner to impeller clearance.

Cheers

 

[chevyjet]

Re: 90 Tohatsu TLDI jet

There are 4 pump sizes and lots of impeller size and pitch options, the pump you have fits 60hp up to about 150 hp with different impellers. You might try the 7 3/16 70 hp impeller but when i did it ran right at 5800 and hit the rev limiter often at WOT, if you are above 3000 feet it would work good.

 

[lots of boats]

Re: 90 Tohatsu TLDI jet

The difference between a 7 3/16, and a 7 3/8 doesn't seem like enough to prevent the motor from being able to get up to recommended rpm at wot. Where on the impeller do I find the pitch stamped.

Thanks

 

[chevyjet]

Re: 90 Tohatsu TLDI jet

Thats the size not the pitch, and ya it makes a big difference. It will be stamped near the shaft hole on the top or bottom.

 

[lots of boats]

Re: 90 Tohatsu TLDI jet

Just to clarify this. For any given diameter impeller is more than one pitch available?

I have bought impellers for other jet outdrives, and have never been offered a choice other than diameter.

 

[chevyjet]

Re: 90 Tohatsu TLDI jet

There is different pitch in the 7 and 3/8 size for the 115s and another for the V6 150s.

 

[lots of boats]

Re: 90 Tohatsu TLDI jet

I bought that jet and 90tldi as a package from a dealer, it is an A model I think, has the elbow on the air pump that either broke off or plugged...
So, for the 90TLDI, only one choice of impeller. 7 3/8. Will not turn up past 4800. So that is why you thought you were not getting 90hp out of your motor. But if you went to the 7 3/16, you could get full power.

 

[chevyjet]

Re: 90 Tohatsu TLDI jet

You should try the smaller impeller, or cut about 1/4 inch of the TOP of the blades at the same angle as the factory machining. The ones I was messing with were all B models but it sounds like the As are just as gutless.

 

[whitewater90]

Re: 90 Tohatsu TLDI jet

I had the same problem with not getting full RPM on a Nissan 90 TLDI B, I took 3/8" off the top of the 7 3/8" with a lathe, now i get 5400 RPM with a cold engine, if i rember corectly the top of the impeller is at a 45* angle so it east to do the work, or take it to a good machine shop.

 

[lots of boats]

Re: 90 Tohatsu TLDI jet

You must have had an A model at some point, I think they changed the elbow on the B model air compressor because they plugged. The big problem with the jet was plugging up the lines, the dealer actually pointed this out when I bought the jet package. My impeller is 7 3/8. I need to look at the impeller on an an old 75 hp Yamaha jet I have. If it is the same housing it should fit into the pump housing for the TLDI and spin up a little more because of the wear on it?

 

[whitewater90]

Re: 90 Tohatsu TLDI jet

Just run the Yamaha, least it will always get you home. The yamaha 75 will be using the 7 3/16 so it will work for you.
Yes they changed the fitting on the air pump between the A and B model, the B has a streaght fitting so anything in the cooling water will get stuck in the pisser which is harder to get to get cleaned out.

 

[lots of boats]

Re: 90 Tohatsu TLDI jet

The only way you can clean out the pee tube if a small twig or other solid debis gets lodged against the fitting where the hose shoves on at the base of the cowling, is to pull off the hose. You can push twigs up and down with a wire all day long and they can't get out past the fitting. The problem with pulling the hose off is that it is difficult to get it pushed back on the fitting. I was thinking it might make more sense to pull the hose off farther back, maybe at the pump, and blow the debis back.

 

[chevyjet]

Re: 90 Tohatsu TLDI jet

If you have trouble with the pisser geting pluged pull the hose off and drill a new hole farther up the lower cowl so you can get at it and reinstall, there is so much crap packed under the cowl on the tldi`s that you just can`t get at it.

 

[chevyjet]

Re: 90 Tohatsu TLDI jet

Another thing i forgot to tell you is that you should not spend the money on stainless 4 blade impellers on these moters cause they cannot pull them even cut down, and thats alot of money to wast.

 

[whitewater90]

Re: 90 Tohatsu TLDI jet

The aluminum Impeller will out last the powerhead on these 90 Nissans anyway. Be careful wen Jetboating with one of these things in ruff water, the TPS can take a Vacation wen you need power to get out of a tight spot, packing a winch is a good Idea also

 

[chevyjet]

Re: 90 Tohatsu TLDI jet

HAHAHHA thats why i took the jet off my TLDI i could not ever count on it to rev when it was suposed to, some times all 3 lights would come on 20 times a day and it almost got me killed once.

 

[lots of boats]

Re: 90 Tohatsu TLDI jet

I see you guys are still at it. I think we agree, the 90 TLDI wouldn't pull a 73/8 impeller, I has hoping it would do OK with a smaller load, but hadn't thought about the TPS shutting the system down in rough water, just when power is critical. Not much use in a mountain stream full of rocks and log piles. I think I'll look at some of the aftermarket stuff for my older motors. New topic?